1. Field of the Invention
The present invention relates to an electronic apparatus and, more particularly, to an electronic apparatus which uses a detachable memory card such as, for example, an external memory device and in which a power source is supplied from the apparatus main body to the memory card for a period of time when the memory card is loaded and, in the case where the memory card is unloaded, the memory content in a memory element of the memory card is backed up by a backup power supply element in the memory card.
2. Related Background Art
Hitherto, an apparatus using a memory card as a memory medium has been known as a portable electronic apparatus, particularly, as a handy terminal, a portable word processor, or a personal computer.
In the case of using a memory card in a conventional portable terminal apparatus, when the memory card is not loaded into the portable terminal apparatus, data in the memory is held by a lithium battery provided in the memory card. When the card is loaded, a power source is supplied from the portable terminal apparatus, thereby preventing the consumption of the electric power of the lithium battery.
However, in the above conventional apparatus, an exchange period of time of the lithium battery is set in correspondence with the memory capacity of the memory card so as not to extinguish the data in the memory card. Since such a period of time is generally set on a unit basis of a half year or one year, there are the following drawbacks.
(1) If the exchange period of time of the lithium battery is set on the assumption that the power source is supplied from the portable terminal apparatus, when the loading time is exceptionally short, there is a fear that data may be extinguished due to a voltage drop of the lithium battery when the exchange period of time is a half year or longer.
(2) On the contrary, if the loading time is long and an electric power consumption of the lithium battery is small, the battery must be exchanged at a time near a predetermined exchange period of time in spite of the fact that there is no need to exchange the battery which still has sufficient capacity, because the apparatus does not have the means for detecting the electric power consumption of the battery. Such an exchange operation is troublesome.
A deviation of the substantial exchange period of time of the lithium battery due to the loading time corresponds to an error of 8 to 25% for the battery exchange period of time when it is assumed that the loading time is one to three hours per day.
Therefore, there is a problem such that if the user erroneously discriminates the exchange period of time of the lithium battery of the memory card, the significant data is extinguished.